This invention relates to a storage apparatus.
There are cases where an amount of data is reduced for its storage in order to decrease a cost of a medium for storing the data. For example, file compression contracts data segments having the same content in one file, to thereby reduce the data amount. Deduplication contracts data segments having the same content not only in one file but also among files, to thereby reduce an amount of data in a file system and a storage apparatus.
In the following description, a data segment that is the unit of deduplication processing is referred to as “chunk”. Logically cohesive data that is the unit of storage in a storage device is referred to as “content”. Content can be a normal file, a file in which normal files are assembled, for example, an archive file, a backup file, a virtual file, or a volume file, a part of a file, or a part of a volume.
The background art of the technology of this invention includes U.S. Pat. No. 5,990,810 A. In U.S. Pat. No. 5,990,810 A, there is disclosed a method of efficiently storing data by executing duplication determination in a case where content is to be stored in a storage apparatus from a host computer over a network to determine, for each chunk, whether the chunk is already stored in the storage apparatus, and then transmitting only chunks that are not stored yet to reduce the amount of data transferred.